Method for preparing covering sheets or strips in crepe rubber, for use in the production of shoes

Abstract

The present invention relates to a method for preparing covering sheets or strips in crepe rubber, wherein the creped appearance is retained in the finished product such as shoes made from such sheets or strips, wherein the pieces of rubber are introduced between the cylinders of a mixer of which the relative tangential speed and the variation of the space therebetween ae adjusted to obtain in cold conditions a natural crepe rubber without the arrangement of the molecules in the rubber being broken; the tongue or coagulum thus obtained is run between the cylinders as different ingredients (sulphur, coloring agents, accelerator) are sprinkled over its surface; then said coagulum thus filled and creped is calendered until the required thickness is reached evenly; said coagulum is finally applied to mounting the product such as a shoe, which is thereafter vulcanized in an autoclave.

What is claimed is: 
     
       1. Method for preparing covering sheets or strips in crepe rubber, wherein the creped appearance is retained in the finished product such as shoes made from such sheets or strips, said method consisting in introducing substantially parallelepipedal and relatively flat pieces of natural rubber of around half a cubic decimeter, between the cylinders of an external mixer, turning at different tangential speeds, the relative space between the cylinders being reduced after each run therethrough of the resulting rubber coagulum, process wherein: the relative tangential speed of the cylinders and the variation of the space between them are so adjusted as to obtain the formation of "crepe" or "crinkled" natural rubber without breaking the "nerve" of the material,   the pieces thus mechanically mixed, form a sort of a "tongue" or coagulum which, immediately its rear end drops out of the cylinder, is re-introduced therethrough by its front end;   various ingredients, preferably in pulverulent form, such as sulphur, coloring materials, accelerator, are sprayed over the coagulum, on at least some of these runs through the cylinders and penetrate into the rubber by the conjugated mild actions of compression and differential friction exerted by the cylinders;   and the colored, sulphurated and accelerated coagulum thus treated, whose thickness is between 10 and 15 mm, is calendered on smooth and permanently cooled rollers turning at the same tangential speed, in a plurality of successive runs, the distance between these calendering rollers being progressively reduced until the thickness of the resulting strip or sheet is between 1 and 5 mm depending on the use it is wanted for;   and finally, wherein the shoe or other product is mounted with the side strips and sole sheets cold-creped as indicated hereinabove, then it is vulcanized in an autoclave in conditions of temperature, pressure and duration appropriate to the special nature of the basic rubber used.